1 /* 2 3 x86 function call convention, 64-bit: 4 ------------------------------------- 5 arguments | callee-saved | extra caller-saved | return 6 [callee-clobbered] | | [callee-clobbered] | 7 --------------------------------------------------------------------------- 8 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] 9 10 ( rsp is obviously invariant across normal function calls. (gcc can 'merge' 11 functions when it sees tail-call optimization possibilities) rflags is 12 clobbered. Leftover arguments are passed over the stack frame.) 13 14 [*] In the frame-pointers case rbp is fixed to the stack frame. 15 16 [**] for struct return values wider than 64 bits the return convention is a 17 bit more complex: up to 128 bits width we return small structures 18 straight in rax, rdx. For structures larger than that (3 words or 19 larger) the caller puts a pointer to an on-stack return struct 20 [allocated in the caller's stack frame] into the first argument - i.e. 21 into rdi. All other arguments shift up by one in this case. 22 Fortunately this case is rare in the kernel. 23 24 For 32-bit we have the following conventions - kernel is built with 25 -mregparm=3 and -freg-struct-return: 26 27 x86 function calling convention, 32-bit: 28 ---------------------------------------- 29 arguments | callee-saved | extra caller-saved | return 30 [callee-clobbered] | | [callee-clobbered] | 31 ------------------------------------------------------------------------- 32 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] 33 34 ( here too esp is obviously invariant across normal function calls. eflags 35 is clobbered. Leftover arguments are passed over the stack frame. ) 36 37 [*] In the frame-pointers case ebp is fixed to the stack frame. 38 39 [**] We build with -freg-struct-return, which on 32-bit means similar 40 semantics as on 64-bit: edx can be used for a second return value 41 (i.e. covering integer and structure sizes up to 64 bits) - after that 42 it gets more complex and more expensive: 3-word or larger struct returns 43 get done in the caller's frame and the pointer to the return struct goes 44 into regparm0, i.e. eax - the other arguments shift up and the 45 function's register parameters degenerate to regparm=2 in essence. 46 47 */ 48 49 #include "dwarf2.h" 50 51 /* 52 * 64-bit system call stack frame layout defines and helpers, for 53 * assembly code (note that the seemingly unnecessary parentheses 54 * are to prevent cpp from inserting spaces in expressions that get 55 * passed to macros): 56 */ 57 58 #define R15 (0) 59 #define R14 (8) 60 #define R13 (16) 61 #define R12 (24) 62 #define RBP (32) 63 #define RBX (40) 64 65 /* arguments: interrupts/non tracing syscalls only save up to here: */ 66 #define R11 (48) 67 #define R10 (56) 68 #define R9 (64) 69 #define R8 (72) 70 #define RAX (80) 71 #define RCX (88) 72 #define RDX (96) 73 #define RSI (104) 74 #define RDI (112) 75 #define ORIG_RAX (120) /* + error_code */ 76 /* end of arguments */ 77 78 /* cpu exception frame or undefined in case of fast syscall: */ 79 #define RIP (128) 80 #define CS (136) 81 #define EFLAGS (144) 82 #define RSP (152) 83 #define SS (160) 84 85 #define ARGOFFSET R11 86 #define SWFRAME ORIG_RAX 87 88 .macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1 89 subq $9*8+\addskip, %rsp 90 CFI_ADJUST_CFA_OFFSET 9*8+\addskip 91 movq_cfi rdi, 8*8 92 movq_cfi rsi, 7*8 93 movq_cfi rdx, 6*8 94 95 .if \save_rcx 96 movq_cfi rcx, 5*8 97 .endif 98 99 movq_cfi rax, 4*8 100 101 .if \save_r891011 102 movq_cfi r8, 3*8 103 movq_cfi r9, 2*8 104 movq_cfi r10, 1*8 105 movq_cfi r11, 0*8 106 .endif 107 108 .endm 109 110 #define ARG_SKIP (9*8) 111 112 .macro RESTORE_ARGS rstor_rax=1, addskip=0, rstor_rcx=1, rstor_r11=1, \ 113 rstor_r8910=1, rstor_rdx=1 114 .if \rstor_r11 115 movq_cfi_restore 0*8, r11 116 .endif 117 118 .if \rstor_r8910 119 movq_cfi_restore 1*8, r10 120 movq_cfi_restore 2*8, r9 121 movq_cfi_restore 3*8, r8 122 .endif 123 124 .if \rstor_rax 125 movq_cfi_restore 4*8, rax 126 .endif 127 128 .if \rstor_rcx 129 movq_cfi_restore 5*8, rcx 130 .endif 131 132 .if \rstor_rdx 133 movq_cfi_restore 6*8, rdx 134 .endif 135 136 movq_cfi_restore 7*8, rsi 137 movq_cfi_restore 8*8, rdi 138 139 .if ARG_SKIP+\addskip > 0 140 addq $ARG_SKIP+\addskip, %rsp 141 CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip) 142 .endif 143 .endm 144 145 .macro LOAD_ARGS offset, skiprax=0 146 movq \offset(%rsp), %r11 147 movq \offset+8(%rsp), %r10 148 movq \offset+16(%rsp), %r9 149 movq \offset+24(%rsp), %r8 150 movq \offset+40(%rsp), %rcx 151 movq \offset+48(%rsp), %rdx 152 movq \offset+56(%rsp), %rsi 153 movq \offset+64(%rsp), %rdi 154 .if \skiprax 155 .else 156 movq \offset+72(%rsp), %rax 157 .endif 158 .endm 159 160 #define REST_SKIP (6*8) 161 162 .macro SAVE_REST 163 subq $REST_SKIP, %rsp 164 CFI_ADJUST_CFA_OFFSET REST_SKIP 165 movq_cfi rbx, 5*8 166 movq_cfi rbp, 4*8 167 movq_cfi r12, 3*8 168 movq_cfi r13, 2*8 169 movq_cfi r14, 1*8 170 movq_cfi r15, 0*8 171 .endm 172 173 .macro RESTORE_REST 174 movq_cfi_restore 0*8, r15 175 movq_cfi_restore 1*8, r14 176 movq_cfi_restore 2*8, r13 177 movq_cfi_restore 3*8, r12 178 movq_cfi_restore 4*8, rbp 179 movq_cfi_restore 5*8, rbx 180 addq $REST_SKIP, %rsp 181 CFI_ADJUST_CFA_OFFSET -(REST_SKIP) 182 .endm 183 184 .macro SAVE_ALL 185 SAVE_ARGS 186 SAVE_REST 187 .endm 188 189 .macro RESTORE_ALL addskip=0 190 RESTORE_REST 191 RESTORE_ARGS 1, \addskip 192 .endm 193 194 .macro icebp 195 .byte 0xf1 196 .endm 197